Hi,
I got curious why it is advised to leave "Automatically adjust brightness" on.
I have an iMac and I got some relief when I switched off automatic brightness and set brightness to 50% at night and to about 55-60% during the day. Lower brightness is uncomfortable to me, maybe because of more reflections from the screen, maybe because of some technologies used at lower brightness. I can only guess.
Without automatic brightness the image seems more stable to me. However, I understand that everything is very subjective in this field and depends on many factors, including even the physical condition at a specific moment.
I'd like to add to the recent discussion about Catalina. I have upgraded and I have a feeling that the drivers have changed (I have Radeon graphics). I still have a strain after some time of working with the text (I only have strain from the text), but it is different. No more dizziness, but there is some burning in the eyes after some time at the iMac. And after maybe 2 to 3 hours the eyes become very tired, like sleepy.
I have experimented a bit and what works best for me: brightness no less than 50%, native resolution 2560x1440, millions of colors in SwitchResX, "Best for external displays" setting in Parallels Desktop and no Coherence mode, 300% scaling in Windows, monospaced fonts like Consolas or Monaco in my work apps, automatic brightness off. I'm still trying different color profiles. Also, some programs are less straining than the others. Safari is the best in this respect, so now I use it instead of Chrome.
But this has not solved my issues, it just gives me more time to work at the computer. So it would really be great to have an app capable of switching off dithering or whatever is straining the eyes on Mac.